With the introduction of 4th generation mobile networks, applications such as high-quality video streaming to the end user becomes possible. However, the expected demand for such services outpaces the capacity increase of the networks. Since there is mostly a capacity bottleneck in the air interface between a base station and user equipment, one of the main challenges for radio resource management is therefore to enforce precise quality guarantees for users with high expectations on service quality. We consider, in this paper, an OFDMA access network with YouTube users, and address the challenge of improving the quality of experience (QoE) of a dedicated user by utilizing the buffered playtime of a YouTube video for scheduling. The advantage of this approach is that scheduling is done according to the instantaneous throughput requirement of the end user application, and not by the network by maintaining average quality-of-service (QoS) parameters. The paper describes the concept and provides a simulative evaluation of the approach in an LTE network to demonstrate the benefits.

The IEEE 802.16 standard specifies two contention-based mechanisms for the OFDMA physical layer to transmit bandwidth requests from subscriber station to base station: the standard mechanism is based on Slotted Aloha with a truncated binary exponential backoff; the alternative one is based on CDMA. This paper describes the CDMA-based contention mechanism and presents an analytic model to compute its performance in terms of delay and consumed resources. The tunable parameters for the CDMA-based random access procedure are the number of ranging subchannels, the number of codes per ranging subchannels, and the detection threshold. An optimal configuration is derived for a given load in terms of the request arrival rate.

Mäder, A., Staehle, D.: Radio Resource Management for the UMTS Enhanced Uplink in Presence of QoS Radio Bearers.Special Issue of Annals of Operation Research on Stochastic Performance Models for Resource Allocati.170, (2009).

The Universal Mobile Telecommunication System (UMTS) offers rate controlled radio bearers for best effort traffic. The purpose of rate control is to maximize resource utilization and concurrently to provide best-effort users with an acceptable grade-of-service. Due to the user behaviour or the used application of a mobile subscriber we distinguish between two types of best-effort users. The time-based users stay for a certain time within the network and download an arbitrary amount of data. Volume-based users leave the network after they have downloaded a specific data volume. The contribution of this work is an evaluation of time-based and volume-based best-effort traffic over rate-controlled DCHs by analytic means and with a detailed packet-level simulation. The results of both approaches are qualitative equal: while the rate control mechanism works effectively for time-based users and allows any rate, the assigned rates for the volume-based users take values between two extremes, either the minimal or the maximal rate.

Most measurement studies in the literature on UMTS focus on scenarios which are set up as ”real” as possible. The focus of this study is the performance and the system behaviour in a nearly ideal laboratory system, such that external influences like other-cell interference or fading are eliminated. We performed experiments on load, throughput and timeliness behaviour with UMTS NodeB hardware of two different brands. The results show different admission control and hardware resource management strategies in high load situations which may impact the performance of applications like voice over IP and the modeling of admission control for dedicated channel radio bearers.

Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. In [1], we have investigated the performance of a crawling peer by means of simulations. Now, we show a time-discrete analysis of the crawling peer’s performance in order to investigate different scenarios and to enable parameter-sensitivity studies for further improvements of the crawling peer’s strategy.

Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. The crawling peer locates content on behalf of mobile peers. It is placed in the wireline part of the mobile network and thus, does not suffer from the above mentioned restrictions. The crawling peer is part of a comprehensive mobile P2P file sharing architecture [1] which is based on the popular eDonkey file sharing application. The performance of three querying strategies of the crawling peer is investigated with respect to banning at the index servers and the response time of requests, i.e. the time to find a file. The results show that the selection of an appropriate request strategy for the crawling peer maximizes the probability of locating a file while the probability to be banned by an eDonkey index server is minimized.

P2P file sharing systems account for a high percentage of the traffic volume in the fixed Internet, having exceeded http (WWW) or email traffic [1] [2]. The increasing availability of mobile data networks such as GPRS and UMTS in conjunction with attractive pricing schemes makes P2P file sharing an interesting application also in the mobile context. But the operation of P2P systems in mobile environments encounters several problems, such as a relatively narrow and expensive air interface, highly varying online states (presence) of the subscribers, a hierarchical network structure (GPRS), and limited device capabilities. P2P is a distributed application architecture where equal entities, denoted as peers, voluntarily share resources, e.g. files or CPU cycles, via direct, end-to-end exchanges. In order to share resources, P2P applications need to support two fundamental coordination and control functions: Resource mediation mechanisms, i.e. functions to locate resources or entities, and resource control mechanisms, i.e. functions to permit, prioritize, and schedule the access to resources. Pure P2P architectures are implementing both mechanisms in a fully decentralized manner [3], while Hybrid P2P systems utilize central entities that collect mediation data. An example for a Hybrid P2P system is the eDonkey filesharing protocol, where the index servers collect and distribute file location information about all peers. The desire of mobile network operators is to add value to the P2P data flows and to turn P2P into a service they can charge for. When creating such services operators retain control on traffic and content. However the basic P2P user experience and connectivity should be preserved. In this paper, we describe such a service and analyze its impact on the network usage by means of a simulation.

P2P file sharing is an interesting application in a mobile data network such as GSM/GPRS and UMTS. In particular in mobile environments, operation of P2P systems encounters several problems, such as a relatively narrow and expensive air interface, highly varying online-state (presence) of subscribers, hierarchical network structure, and limited device capabilities. The desire of operators is to add some value to P2P data flows and to turn them into services. At least some control over traffic and content should be possible, while preserving the basic P2P user experience and connectivity. Operation of P2P file sharing services in next generation mobile networks has to suit the needs of users as well as to accommodate the constraints imposed by 3G mobile technology and 3G network operation.